This invention relates to a throttle valve for an internal combustion machine which is mounted on a shaft with a cable line, or other linkage member, for rotating the shaft and with at least one return spring coupled to the cable line, a first detent being between the cable line and the shaft, a first coupling apparatus being between the cable line and the shaft and a positioning motor.
Such a throttle-valve apparatus is known from German Offenlegungsschrift DE-OS No. 37 11 779. The throttle valve of this document is mounted on a shaft which is rotatable by a cable line. The cable line is operated on by a return spring with a force in a direction for closing the throttle valve. The throttle valve apparatus additionally has a first detent between the cable line and the shaft whose engagement, or stop, point can be moved with the help of the cable line so that the throttle valve is moveable between its closing position and the stop position. A coupling apparatus is arranged between the cable line and the shaft which here is disclosed as being a spring. For interrupting a motor torque, for example upon the appearance of loss of traction of a driven tire of a motor vehicle, the throttle valve has a positioning motor which can move the throttle valve. The positioning motor is coupled to the shaft via a second detent whose engagement, or stop, point is adjustable with the help of the positioning motor so that the throttle valve is manipulatable in a closing direction.
A particular disadvantage of this system is that when the throttle valve is driven by the positioning motor, the positioning motor has to continually work against the spring force of the spring which couples the cable line to the shaft. Because the spring force increases with further stress thereon, it is necessary to have a positioning motor that provides a high performance, resulting in an expensive apparatus. In this regard, it is additionally disadvantageous that because the positioning motor must be driven to provide greater forces, a life of the positioning motor is reduced so that safety and dependability when operating the motor vehicle, particularly since this involves an apparatus pertaining to safety such as a throttle valve, is reduced.
Further, it is disadvantageous that the positioning motor, when the throttle valve is manipulated by the cable line, is not also automatically driven so that when it is necessary for the positioning motor to intervene in positioning the throttle valve there is an undesirable delay, which can have disadvantageous consequences in a controlled behavior situation, for example, when controlling slippage of a motor vehicle.
It is an object of this invention to provide a throttle valve apparatus which, in an uncomplicated and cost effective system, improves safety and dependability during operation of a motor vehicle and which includes a positioning motor whose operation is relieved from return forces on a throttle-valve.
According to principles of this invention, a throttle-valve apparatus includes a first coupling apparatus which is a first coupling having a changeable, or releasable, driving engagement whereby the driving engagement is greatest in an immediate area of a moveable, or changeable, engagement, or stop, point.